The present invention relates generally to control apparatuses for internal combustion engines, and more particularly to a combustion control apparatus for an internal combustion engine with an exhaust purifier such as a particulate filter and a NOx trap, which is configured to decrease an excess air ratio of the engine, and to raise an exhaust gas temperature of the engine, without increasing exhaust smoke.
In recent years, there have been disclosed various techniques of raising an exhaust gas temperature to activate an exhaust purifier for an engine with an exhaust purifier in an exhaust gas passage. One such technique is disclosed in Japanese Patent Provisional Publication No. 2000-320386, especially in paragraphs [0106] through [0111]. In this technique, a basic fuel injection quantity to produce a desired engine torque is calculated in accordance with an operating condition of the engine. The basic fuel injection quantity of fuel is supplied to a cylinder of the engine by multiple fuel injections near top dead center (TDC).
On the other hand, a known method of removing nitrogen oxides (NOx) from exhaust gas employs a NOx trap. The NOx trap traps NOx in oxidizing atmosphere and releases NOx in reducing atmosphere. The NOx trap also removes from exhaust gas and traps sulfur content in oxidizing atmosphere. Accordingly, a known method of releasing NOx and sulfur content trapped in NOx trap to regenerate the NOx trap is to decrease an excess air ratio to decrease an exhaust air-fuel ratio. In general, the exhaust gas temperature is raised to promote dissociation of sulfur content in addition to decreasing the exhaust air-fuel ratio, during the NOx trap releasing sulfur content.